Horn



E. B. MALLORY 1,771,052

HORN

July 22, 1930.

Filed April 29, 1924 Fig.1.

00000 000000 oooo-o ooooo 0000 o o o o 00 oooooooooo 4 o-oooo oooo-o-oooo 00000 0000 0 0 0 0 00 0000 0 0 0 0 0 o o oo o - 00 1112' 0000 AAAZ oo0% v 000 00 o oo 0000 00000 oo-oou 00000 INVENTOR Patented July 22, 1930 UNITED STATES PATENT OFFICE EDWARD B. MALLORY, OF TENAFLY, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE ELEC- TRIC & MANUFACTURING COMPANY,

A CORPORATION OE PENNSYLVANIA HORN Application filed April 29,

Still another object of my invention is to provide a sound-reinforcing horn of material that is better adapted to be conduction and amplification of sound.

Still another object of my invention is to provide a sound-reinforcing horn of a suit able plastic material in which is incorporated strengthening and reinforcing means.

In the conversion of vibratory electric currents into sound, it has been found desirable to convert he vibratory electrical energy into the energy of vibration of a diaphragm; to convert this energy into vibratory motion of adjacent air particles; and to pass this vibraao tory motion through a horn which is adapted to amplify, direct and control it.

Hard rubber has further been found es pecially desirable for the construction of horns because of the fact that a considerable 5 amount of control of its vibrational qualities is possible. It has been found, byexperiment, that vibration or resonance of the body ma terial of a horn. is undesirable, since it usually occurs at some particuular resonant fre quency, and that the vibration should be confined to the air column within the horn. This phenomenon of body resonance is troublesome in the case of metal horns, since the metal, having a high modulus of elasticity,

vibrates readily. Wood. likewise, has a similar resonant quality. This undersirable resonance can be avoided in, the case of hard rubber horns by modifying the physical character of the material itself through changes in its composition.

1924. Serial No. 709,881.

Hard ruber is customarily produced by compounding together gum rubber, sulphur, and some inert filler material, such as gas black, zinc oxide, clay and others of a wide variety of substances. This compound is then shaped and vulcanized.

As much as one part of sulphur can be incorporated into two parts of rubber. This produces a hard rubber which is exceedingly hard and brittle. The minnium amount of sulphur to produce a vulcanized rubber is approximately 3% of the rubber. Such a proportion has the characteristic properties of soft rubber. Variation of the sulphur content between these limits produces a rubber of various degrees of hardness.

The very hard rubber containing amaximum amount of sulphur has been found to have resonant and vibrational properties similar to those of wood and metal. By reducing the sulphur content slightly to about one part of sulphur to four partsof gum rubber, a rubber is obtained which is reasonably hard but which lacks the extreme brittlenessof ordinary hard rubber and which also lacks its resonant qualities.

Both empirical data and scientific investigation have proven that a horn having a shape similar to that of the morning glory is particularly desirable for use with a vibratory diaphragm. This shape is substantially that of an exponential curve and it gives particularly satisfactory conduction and amplification of sound. The shape has been most readily produced by the molding of the plastic materials previously mentioned.

7 When a horn is made of the less hard rubber compound which is desirable and put into service, however, it has been found that, under conditions of slightly elevated temperatures, such as occur over steam radiator, for instance, the rubber does not satlsfactorily hold its shape. but gives and bends under the pressure of its own weight. The resulting deformation very largely takes place at the small end of the horn where the stresses are greatest and the cross section of material least, injuring the appearance of the horn and its sound conveying and amplitying properties.

and

As a means of overcoming this difficulty, I have produced a horn structure composed of rubber of the previously outlined degree of hardness, in which I have inserted a reinforcing means, and to which I have attached a ferrule. The reinforcing means supports the shape of the horn structure and the ferrule adapts it to be attached to the frame or stand which carries the vibrating diaphragm and the elect-ro-magnetic actuating means.

The insert is placed at the small end of the horn where the resonant properties of the material are of less importance and whe e the stresses are highest. By its presence, it holds this more highly stressed portion of the structure to the proper shape and thereby allows the use of such a horn in locations where it previously was unusable because of its failure to hold its shape.

Other objects and structural details of my invention will be apparent from the following description when read in connection with the accompanying drawings, wherein:

Figure 1 is an elevational view of a loudspeaker device with a horn equipped according to my invention.

Fig. 2 is a cross-sectional view of a horn constructed according to my invention in which a reinforcing insert is attached to the ferrule.

Fig. 3 is a cross-sectional view of a. horn constructed according to my invention, with a ferrule having a strengthening skirt sun rounding the lower portion of the horn, and also an insert molded within the horn, and

Fig. 4 is a cross section on the line IVIV of Fig. 3.

5 is a cross sectional view taken along the line VV of Fig. 3.

In Fig. 1 is shown a loud-speaking device comprising a horn 1, a vibrating diaphragm 2, an electromagnetic actuating means 3 and a frame and stand 4. Fig. 2 shows asection of the lower portion of the horn 1 of Fig. 1. The wall of the horn 1, which is of hard rubber. constitutes a sound-conveying chan nel. The horn is provided with a ferrule 5 and a reinforcing metallic insert 6.

In Fig. 3 is similarly shown a portion of a horn of hard rubber having a ferrule 7 and a reinforcing insert 8. i

In the construction of mv invention, each of the inserts 6 and 8, in Figs. 2 and 3. respectively. is prepared of perforated material. It may be formed of a sheet of metal perforated and rolled to proper size and shape. or it may be drawn of metal to the proper shape without a seam and perforated. The completed insert is adjusted in a suitable mold. The molding composition, such as hard rubber is placed around the insert in. the mold. The ferrule 5 or 7, as the case may he, is next adjusted in proper relative position, the mold closed and the material cured in the customary manner. The presence of the perforations permits the molding comp sition to flow therethrough, and interlock with, the material of the strengthening rt, tl ereby holding it firmly in place.

The shape of the insert is such that it will lie within the body of the horn and the perforations through it permit rubber to flow to the inner surface, thereby completely hiding the insert and producing a horn having a smooth interior and exterior surface.

By this means, I am able to produce a sound-conveying channel suitable for use in connection with a loud-speaking telephonic device that is of greater durability and adapted to use under more severe operating conditions than has been produced by previous methods of construction.

The construction of my invention is particularly adapted to horns of the semi hard rubber, as hereinbefore described, which has had compounded with it such substances as ammonium carbonate, sodium bicarbonate, magnesium carbonate, or similar substances which cause the rubber to assume, during curing, a spongy texture.

This system of construction is also applicable to horn constructions from other plastic materials, su h as celluloid, and I desire that the invention be not limited to rubber or to metal devices.

While I have shown only two embodiments of my invention in the accompanying drawings. it is capable of various changes and modifications without departing from the spirit thereof, and it is desired. therefore, that only such limitations shall be imposed thereon as are indicated in the prior art or in the appended claims.

I claim as my invention:

1. In combination, a horn body of solidified plastic material, a ferrule affixed to the smaller on (1 thereof, and an interior metallic insert in said body adjacent to said ferrule, said insert having a plurality of openings through the wall thereof to accommodate extruded portions of the material of said body.

In combination, a horn body of solidified plastic material, a ferrule attached to the smaller end thereof, and a strengthening in ert in the interior of said body, said insert extending to within said ferrule and having a plurality of openings through the wall thereof whereby it may be bonded to said horn body.

3. In combination, a tapering horn body of hard rubber. and an interior metallic strengthening insert having a plurality of opeuinq's through the wall thereof whereby it may be bonded to said horn body while the latter is in a plasticcondition.

In testimony whereof, I have hereunto subscribed my name this 26th day of March,

EDIVARD B. MALLORY. 

